feat: add OBS recording engine and validation probe

clipbin-obs starts the pinned libobs on a dedicated thread, opens exactly the
bundled plugin allowlist, and records official capture sources through one
hardware encoder into keyframe-aligned Matroska segments. Status reaches
Recording only once the source has a picture and the segment grows on disk.

clipbin-probe lists and verifies hardware encoders and records from a real
capture source, printing status, health and segment events for validation.

crates/clipbin-obs/Cargo.toml

@@ -0,0 +1,17 @@
+[package]
+name = "clipbin-obs"
+description = "Clipbin's recording engine adapter over the pinned libobs runtime."
+version.workspace = true
+edition.workspace = true
+rust-version.workspace = true
+license.workspace = true
+repository.workspace = true
+publish.workspace = true
+
+[dependencies]
+clipbin-core.workspace = true
+libobs.workspace = true
+
+# Raw libobs calls are confined to src/ffi.rs, which opts back in to unsafe code.
+[lints.rust]
+unsafe_code = "deny"